Make pynest installable via pip, split pynest.py into an main program and a library, and move from urllibX to requests

This looks like a fairly extensive change, but its actually rather modest and doesn't include any of my own app-specific code

1. split pynest.py into a main program and a library. this has been done numerous times in various forks. I think my commit is the minimal necessary to make it a useful

2. created a package for the pynest library, and pynest easily installed via pip:

      % pip install git+https://github.com/Tengah/pynest  (or whatever your github repo is)

   it will now be now super easy to add pynest to https://pypi.python.org/

3. convert urllibX to the much simpler and more modern python requests: http://www.python-requests.org/

4. DRY'd set_fan and set_temperature 

feedback welcome